1. Field of the Invention
The present invention relates to an art of a cooling device for vehicle headlights having a Light Emitting Diode (i.e., an LED).
2. Discussion of the Related Art
A cooling device for vehicle headlights having an LED illuminant is widely used in the conventional art. An electric consumption of the LED is advantageously low, but a calorific value of the LED is rather high and the LED is therefore easily to be heated. That is, since the LED is a semiconductor light source, an operating temperature limit of the LED is not sufficiently high and a usable temperature range thereof has to be limited. If the temperature of the LED exceeds the usable temperature range, durability and brightness thereof will be degraded. Therefore, in order to prevent an excessive temperature rise in the LED, a cooling device for the LED is used in the conventional vehicle headlights.
JP-A-2009-087620 describes a headlight for vehicle in which an exothermic LED is thermally connected to a heat sink as a heat dissipation member through a flexible heat-conductive member. In turn, JP-A-2006-164967 describes a vehicular lighting in which an LED is thermally connected to a heat sink through a loop heat pipe. According to the teachings of both JP-A-2009-087620 and JP-A-2006-164967, fins of the heat sink are exposed on the outside of a housing holding the LED.
Further, JP-A-2010-129543 describes a headlight for vehicle in which an LED is placed on an upper face of the heat sink fitted into a center hole formed in a housing. In addition, a cooling fan is disposed outside of the housing underneath the heat sink so that the heat sink can be cooled by the cooling fan through the center hole.
However, the fins of the heat sink thus exposed on the outside of the housing of the LED may enlarge the vehicle headlights taught by JP-A-2009-087620 and JP-A-2006-164967. In turn, the cooling fan thus integrated with the heat sink may also enlarge the vehicle headlights taught by JP-A-2010-129543.
In addition, according to any of the teachings of the foregoing prior art documents, the external shape of the housing may be restricted by the heat sink arranged on a part of a housing wall in the housing. Therefore, it is difficult to arrange an additional element in the housing of the headlight. That is, even if the headlight is required to be integrated with an additional cooling device, an external shape and a flexibility of arrangement of the additional cooling device may be restricted.
The present invention has been conceived nothing the foregoing technical problems, and it is therefore an object of the present invention is to provide a cooling device for vehicle headlights that effectively cools an LED as a light source while ensuring a flexibility of shape of a housing holding the LED.